The invention generally relates to implantable cardiac stimulation devices and to external programmers used in connection therewith and in particular to methods and apparatus for processing and displaying event markers and other diagnostic information detected by an implanted device.
A wide variety of implantable cardiac stimulation devices are provided for surgical implantation into patients. One common example is the cardiac pacemaker. Another is the internal cardioverter defibrillator (ICD). Implantable devices are often configured to be used in conjunction with an external programmer that allows a physician to display information detected by the implanted device. For example, the external programmer may operate to display electrical cardiac signals detected by the implantable device in the form of intracardiac electrograms (IEGMs). An IEGM is a graphic depiction of electrical signals emitted by active cardiac tissue as detected by electrodes placed in the heart. The electrical signals are digitized and recorded with the implanted device along with an indication of the date and time, then transmitted to the external programmer for display thereon, perhaps during a subsequent follow-up session with the physician. Alternatively, the implanted device is controlled to transmit the IEGM signals in real-time during the follow-up session. The external programmer may also be configured to receive real-time surface electrocardiogram (ECG) signals from an external ECG detector, perhaps for display along with contemporaneous real-time IEGM signals transmitted from the implanted device.
The implanted device may also be configured to detect various events, such as paced and sensed events, and to generate event codes representative of the events for transmission to the external programmer. The event codes are detected and stored in the implanted device along with the corresponding IEGM signals and the date and time for subsequent transmission to the external programmer or are detected and transmitted to the external programmer in real-time along with real-time IEGM signals. The external programmer generates event marker icons based on the code and displays the icons along with either IEGM signals, ECG signals, or both. Exemplary event markers are: P for a sensed event in the atria; R for a sensed event in the ventricles; A for a paced event in the atria, and V for a paced event in the ventricles. Along with the event markers, the programmer may also display variable length horizontal lines representative of the length of atrial and ventricular refractory periods associated with the events along with numerical values indicative of measured intervals between atrial and ventricular events, based on still further information recorded and transmitted by the implantable device. The external programmer may also display additional information received from the implanted device such as numerical information identifying the heart rate and the duration of ventricular and atrial refractory periods. Also, the display may provide other event markers as well, such as event markers indicating mode switching events. The implanted device may also maintain counters for counting various events, such as paced and sensed atrial and ventricular event counters, for subsequent transmission to and display using the external programmer.
An exemplary surface ECG display, along with event markers, is provided in FIG. 1. More specifically, FIG. 1 illustrates three ECG complexes (denoted 2, 4 and 6), along with P and R event markers indicating that the atrial and ventricular events are both intrinsic events. For both the P and R events, the display also includes horizontal lines adjacent thereto that indicate the length of the corresponding refractory period. Although not shown in FIG. 1, the external programmer may display additional information received from the implanted device such as IEGM signals.
Such displays of event markers and counters are helpful in permitting the physician to analyze the operation of the implanted device and to diagnose arrhythmias, if any, within the patient. U.S. Pat. No. 5,431,691 to Snell et al. entitled xe2x80x9cMethod and System for Recording and Displaying a Sequential Series of Pacing Eventsxe2x80x9d provides a description of the operation of an exemplary pacemaker and external programmer including a detailed description of the generation, transmission and display of IEGM data and event markers. U.S. Pat. No. 5,431,691 to Snell et al. is incorporated by reference herein.
Although the typical event codes and counters maintained by implantable devices and the typical event marker icons displayed by external programmers are quite helpful to the physician, room for improvement remains. In particular, state of the art implantable devices are being developed utilizing multiple sensing/pacing leads for pacing or sensing at multiple locations within the heart. For example, separate leads may be provided to the left and right atria, as well as to left and right ventricles. In other cases, a single atrial lead may be capable of sensing and pacing in both the left and right atria, and a single ventricular lead may be capable of sensing and pacing in the left and right ventricles. Devices are also being developed which permit sensing or pacing at two or more locations within a single chamber. Eventually, highly sophisticated devices may be developed which permit sensing and pacing at a large number of locations within each chamber of the heart. As can be appreciated, when using such systems, the aforementioned conventional event codes, counters and event marker icons, which typically distinguish only between the atria and the ventricles may not be sufficient. Consider again the display of FIG. 1. The intrinsic events of the ECG complexes 2 and 6 may have been detected only within the right atrium and ventricle whereas the intrinsic events of the ECG complex 4 may have been detected only within the left atrium and ventricle. Yet, the events markers indicate no such distinction been the left and right chamber events. Moreover, because the complexes themselves are derived from a surface ECG, rather than an IEGM, the complexes contain no polarization information that might permit the physician to distinguish between the left and right chamber events.
Accordingly, there is a need to develop enhanced event codes, event marker icons and event counters which accommodate implantable devices capable of separately sensing and pacing in the left or right chambers of the heart, or at multiple locations within a single chamber of the heart. There is also a need to develop improved hardware and software for use within implantable devices and within external programmers for recording, tracking and displaying the enhanced codes and markers. It is to these ends that aspects of the invention are primarily directed.
In accordance with a first aspect of the invention, a system is provided for use in an implantable cardiac stimulation device for generating diagnostic information using enhanced event codes. The enhanced event codes are representative of events detected using a plurality of leads positioned at different locations within the heart, with at least two leads positioned within the atria or with at least two leads positioned within the ventricles. The system includes means for receiving signals representative of electrical events detected at the respective locations of the leads, means for generating stimulation signals using selected leads, and means for generating location-specific event codes representative of events occurring at the respective locations of the leads. The location-specific event codes correspond to the arrangement of leads and hence include at least two distinct event codes associated the atria or at least two distinct event codes associated with the ventricles. The system also includes means for transmitting the location-specific event codes to an external programmer for display thereon.
In accordance with a second aspect of the invention, an external programmer is provided for use with an implantable cardiac stimulation device for displaying diagnostic information received from the stimulation device using enhanced event marker icons. The external programmer includes means for receiving location-specific event codes transmitted from the stimulation device and means for generating graphic displays of location-specific event marker icons representative of the event codes, with a distinct location-specific event marker icon associated with each distinct location-specific event code. The location-specific event codes provided by the stimulation device correspond to the arrangement of leads of the stimulation device, which includes at least two leads in the atria or at least two leads in the ventricles.
By employing the enhanced location-specific event codes and event marker icons, the diagnostic information provided by the stimulation device and displayed by the external programmer thereby distinguishes events sensed in the left atrium from events sensed in the right atrium and distinguishes events sensed in the left ventricle from events sensed in the right ventricle. If separate sensing locations are provided within each of the four chambers of the heart, the diagnostic information distinguishes electrical events occurring in any particular chamber of the heart from all other chambers of the heart. If multiple sensing locations are provided within a particular chamber of the heart, the diagnostic information distinguishes among electrical events occurring at each of the various locations within the chamber. Location-specific event counters may be provided for separately counting events occurring at the respective locations of the leads so as to permit, for example, display of location-specific event histograms. The stimulation device and external programmer thereby provide more effective tracking of electrical events within the heart and permit more sophisticated displays of diagnostic information.
In one specific example, wherein the stimulation device has pacing/sensing leads within each of the four chambers of the heart, the external programmer displays PR and PL event marker icons representative of sensed events in the right and left atria, respectively, and RR and RL event marker icons representative of sensed events in the right and left ventricles, respectively. If the stimulation device is capable of pacing in either the left ventricle, the right ventricle, or both ventricles simultaneously, the external programmer displays VL, VR, and VD event marker icons, respectively. If the stimulation device is also capable of pacing in the left and right atria, the external programmer additionally displays AL, AR and AD event marker icons, respectively. For stimulation devices capable of pacing or sensing at multiple locations within a single chamber, additional subscripted indices are employed indicating the specific location within the chamber. A vertical tick mark is displayed by the external programmer adjacent the each event marker icon to indicate the exact time of the corresponding event. If an intrinsic event sensed in one chamber triggers a stimulation event in another chamber, the external programmer displays two vertical tick marks adjacent to one another along with a pair of event marker icons identifying the sensed and triggered events. Horizontal lines are displayed to indicate the duration of corresponding refractory periods. The event marker icons are displayed adjacent surface ECG signals or IEGM signals, or both. Separate location-specific IEGM signals may be displayed, including, for example, a separate IEGM signal per chamber. The external programmer may also be programmed to display location-specific histograms, such as one histogram for right atrial intrinsic events as a function of heart rate and another histogram of left atrial intrinsic events as a function of heart rate.
Other objects and advantages of the invention are achieved as well. Method embodiments of the invention are also provided.